Morphological features and melting behavior of nanocomposites based on isotactic polypropylene and multiwalled carbon nanotubes

Abstract

Nanocomposites based on low molar mass isotactic polypropylene (iPP) and a low concentrations (1-2 wt %) of multiwalled carbon nanotubes (MWCNTs) were studied using thermal analysis, optical and electronic microscopy, and X-ray diffraction/scattering techniques. It was first determined that MWCNT decrease induction time and act as nucleating agents of the iPP crystals during nonisothermal crystallization. One of the consequences of the nucleation effect was that the original spherulitic morphology of iPP was transformed into a fibrillar-like. The corresponding long period of the original well-defined lamellar structure slightly increased suggesting the formation of thicker crystals in samples containing MWCNT. The nature of the a-iPP crystalline structure was not affected by MWCNT. After nonisothermal crystallization, two melting endotherms were present during thermal scanning of the iPP/MWCNT nanocomposites their proportion changing with the heating rate. After resolving the total DSC signal in its components using MDSC, the overall evolution of such behavior could be explained in terms of the melting/recrystallization mechanism.

Surfactant assisted processing of carbon nanotube/polypropylene composites: Impact of surfactants on the matrix polymer

“…The morphology of semicrystalline thermoplastics is known to affect the mechanical properties to a great extent. Numerous studies have investigated the effect of CNT on the crystallization of PP and it is widely accepted that CNT act as nucleating agents for PP 14, 25–31. The intention of this study is not to add one more set of affirmative results of the nucleating ability of CNT in PP, rather the effect of the surfactant on the crystallization of the nanocomposites is of interest.…”

Effects of carbon nanotubes on polymer physics

“…202 An early paper by the present author suggested that nanotubes favored the beta phase in isotactic polypropylene based on multiple endotherms in DSC experiments 203 while other papers suggested the alpha form was favored. [204][205][206][207] Nanotubes can induce complicated melting-recrystallization phenomena, indicating that claims about polymorphism in isotactic polypropylene must be substantiated with X-ray diffraction measurements casting significant doubt on the conclusions reached by the present author in the early paper. Recent papers describe a method where isotactic polypropylene in dichlorobenzene or high density polyethylene/ultrahigh molecular weight polyethylene was infiltrated into a nanotube aerogel which in turn led to some of the gamma crystalline form 208 or monoclinic (vs. the more typical orthorhombic) form, 209,210 respectively.…”

Non‐isothermal crystallization of Ziegler Natta i‐PP‐graphene nanocomposite: DSC and new model prediction

“…Therefore, research on this topic is constantly being conducted. The current nanofillers include graphite, single and multi‐walled carbon nanotubes (SWCNTs and MWCNTs), and graphene oxide (GnO) . Amino‐functionalized MWCNTs, in particular, have improved the fracture toughness and strain energy as well as flexural strength and stiffness of the base polymer …”

“…The related published work on crystallization deals with i ‐PP‐CNT, i ‐PP‐montmorillonite and i ‐PP‐calcium carbonate, i ‐PP‐exfoliated graphite, and i ‐PP‐GnP nanocomposites . We focus, as summarized above, on nucleating an agent‐free i ‐PP‐GnP nanocomposite.…”